Method and system for miniature passive RFID tags and readers

ABSTRACT

This invention makes possible small size, long range, reliable, low-power, low-cost RFIDs fulfilling the needs of the industry and the roadmap set for RFID, as by Walmart and the DoD. Tag energization and data communication take place by independent means. The invention employs low-power communication means, such as ultra wideband (UWB), for transfer of data between Tag and Reader, and relatively high power narrowband means to remotely energize the Tag. Said means of powering and communication mechanisms, further, are independent of the underlying process, or technology, of implementation of the Microchip on the Tag, as well as from the transceiver technology aboard the Reader. As such, they provide an ideal method and system by which to power and communicate with RFIDs, through cycles of evolution and changes in physical implementation technology.

CROSS REFERENCES

Priority is hereby claimed from Provisional Patent Application No.60/582,988, Filing or 371 (c) Date: Jun. 25, 2004, Confirmation No.2760. A copy of PPA is enclosed for reference.

This application is a Continuation of U.S. patent application Ser. No.11/165,921, filed Jun. 25, 2005, now U.S. Pat. No. 8,089,344, which inturn claims priority from Provisional Application No. 60/582,988, filedJun. 25, 2004.

GOVERNMENT CONTRACT/FEDERAL R&D

None. Not Applicable.

FIELD OF THE INVENTION

Field of the invention is that of contactless passive RFIDs. Contactlesspassive RFIDs are comprised of three basic components: the RFIDMicrochip, typically being an integrated circuit (IC), hereinafterreferred to as “Microchip”, RFID antennas to which are attached theseMicrochips, hereinafter referred to as “Antenna”, and RFID readers, alsoknown as interrogators, energizers or scanners, hereinafter referred toas “Reader” or “Reader subsystem”. The Microchip and Antenna, attachedtogether, comprise an RFID tag, often also referred to as transponder,or inlay, hereinafter referred to as “Tag”. In the industry the Tagalone, for brevity of statement, is in usage often referred to as“RFID”. Where the word antenna is not capitalized, hereinafter, it shallnot be intended to refer to the Antenna of the RFID Tag, but that of theRFID Reader or to other antenna. Optionally, a battery or other powerstorage device may be added to the Tag, and in this case the Tagsgenerally are referred to as battery-assisted. The trio of Microchip,Antenna, and Reader is interfaced to the inventory management subsystemof the enterprise software system of an organization via the Reader,through one or more of the wireline or wireless communication ports ofthe Reader.

BACKGROUND OF THE INVENTION

RFIDs are slated to replace bar codes that have been in use over thepast several decades and are widely expected to become ubiquitous overthe next ten years. The pace transition from bar code to RFID will befaster particularly as regards newly manufactured items, and theapplication RFID will extend far beyond the initial sectors of economywhere it starts. They are destined be used in a greater number ofapplications and in greater volume in the future. In time they willbecome pervasive in the economy of industrialized nations, thendeveloping nations, and then currently partly developed orunder-developed nations joining the ranks of the former. Areas ofapplication for RFIDs include the following and encompass most of theeconomy:

RFIDs contain information about the product to which they are attached,information which in the future will go beyond that presently containedon a bar code. This has typically included an electronic product code,but will in the future include the information that presently stands inthe data base of an inventory management system of an organization wherethe RFID Reader transmits the electronic product code it receives fromthe Tag, such as manufacturing and transit history, when and where made,product epedigree for traceability of constituents, options, features,etc., price history as during promotions etc.

As they are intended to steadily replace bar code usage, the roadmap setfor RFID in the industry, as by the MIT Auto ID Center, its successororganization EPCglobal, Walmart and other large retailers, as well asthe DoD is that of item-level tracking.

Operation of the RFID by means of electromagnetic coupling of energy andthen reflection is commonly referred to as a backscatter system.Following the power coupling, the RFID Microchip comes alive for a brieftime during which it is thus able to transfer its information to theReader. The process may be repeated as necessary. Some RFIDs may bedesigned as read-only, while others allow both reading and writing.Write-once, read-only RFIDs would have their information recorded attime of manufacture or shortly thereafter and are used in applicationswhere the information regarding the item to be tracked is not expectedto be changed. Read-and-write RFIDs can have their information read aswell as altered by the Reader. A class of items in this category toserve as an example would be those under warranty, where the name of thebuyer (as well as the serial number of the product) could be recorded onthe RFID for easy future reference.

Active, or battery-assisted passive, RFIDs are more bulky and expensive,and are used in applications where either the increased cost warrantstheir use or where the RFID in its passive state is in practiceinadequate, as is often the case, but cannot be used in a great numberof applications where cost or sheer bulk would prohibit it, such as agreat many items on the supermarket shelf.

PRIOR ART

Passive RFIDs have no power source, and are intended as minimal costitems, more or less disposable, for high volume item-level tracking andsimilar applications. As such the challenge in engineering them isproviding energy to the RFID Tag and reliably communicating with it,being the coupling, or transfer, to of enough power to the passive RFIDto energize it, and allow its Microchip to transmit its informationcontent, typically stored in its digital nonvolatile memory on-board, tothe Reader. In order to do so, the RFID Microchip, with millimeterdimensions is connected to and placed upon a sheet containing a flatcoil, which sheet also serves as the carrier for the Microchip. Thissheet-Antenna and the Microchip together constitute the RFID Tag. Thedimensions of the coil are much larger than the RFID Microchip and thearea is typically a few square inches, currently in the RFID industry,or when smaller, the range is so low as to limit its application. Thissheet and its Microchip constitute the RFID Tag to be placed on items orproducts for identification or tracking. The combination of the sheetand the coil constitute one unit and are commonly referred to in theRFID context as “Antenna”, whether or not the coupling iselectromagnetic waves. The energy is magnetically, capacitively orelectromagnetically coupled by a Reader or powering device onto theAntenna and thence to the RFID Microchip. In the longest range RFIDsystems electromagnetic waves are used, typically in the UHF(specifically around 900 MHz) or microwave (specifically around 2.45GHz) portion of the spectrum.

Passive RFIDs have no power of their own and being wireless, have to bepowered remotely. With current passive RFID technology with the longestrange possible, energization and data communication takes place over thesame band, typically using carriers in the UHF or microwave region ofthe frequency spectrum, in particular 902-908 MHz (in Europe869.4-869.65 MHz) and 2.4-2.4835 GHz. RFID Microchips, comprisedtypically of integrated circuits, containing stored information indigital form, are attached to a flat sheet on which has been printed acoil Antenna. This Antenna is electrically terminated on the Microchip.Through the Antenna the Microchip is energized by the Reader which,emitting radiation, couples energy to it, enabling it to go from sleepmode to awake mode. To transmit its stored information, then, to theReader, the Microchip alters the level of energy that it reflects andabsorbs, in the field that is directed at it by the Reader. It does soby controlling the termination impedance to of the Antenna. Thus forcommunicating digital information, consisting of ones and zeroes, theTag alternately mirrors back the energy directed at it from the Reader,which process is referred to as backscatter. An elegant design for itstime, to-day with the demands placed on RFID performance and the widerscope requirements generally in the 21^(st) century, the backscattersystem due to a number of shortcomings fails to provide for theindustry's needs. These shortcomings are overcome in great measure inthe present invention. These shortcomings are encountered in practiceand widely known. They are furthermore verified by independent testlaboratories such as RFID Alliance Labs and published in the RFIDJournal. They include the following.

SUMMARY OF SHORTCOMINGS OF PRIOR ART

-   Large Tag size—typically 4 inch by 4 inch, thus cannot fit on many    small items, or when small have a short range-   Low range—even with large Tag size, typically under 20 ft and only    in ideal conditions, suspended in free space-   Considerable path loss of signal—The energy has to suffer path loss    twice, once from Reader to Tag, and a second time, reflected, from    Tag to Reader, each time undergoing this loss in proportion to the    inverse square root of the distance in free space-   Inability to operate reliably without a direct path between Tag and    Reader-   Orientation sensitivity—Tag needs to be properly oriented towards    Reader-   Low reliability and dependability of operation, for example in    motion—up to 50% read failure on a warehouse conveyor belt-   Low mechanical integrity—Large flexible Antenna when bent causes    micro cracks in the Microchip mounted on it as widely known in the    industry, resulting in 20-40% failures or intermittent operation-   No radiolocation or ranging ability—Lack of method or system to    determine local position of Tags

The dimensions of the coil, hence the sheet on which the coil isaffixed, are too large to enable item-level tracking. With small Tags,the range is too low for Reader and Tag to operate effectively.

Specific frequencies used in the RFID industry thus far are 110-140 kHz,4.91 MHz, 13.56 MHz, 800-900 MHz (UHF), 2.45 GHz (microwave). Thefrequency bands on which RFID systems generally fall into three ranges:low frequency (LF), being 30-300 kHz; high frequency (HF) being 3-30MHz; ultra high frequency (UHF) being 300 MHz-3 GHz.

OBJECTS AND ADVANTAGES OF THE INVENTION

The classification of RFID systems by the Auto-ID center, and itssuccessor organization EPCglobal is stated below. The RFIDs in thisinvention are intended to perform almost all these.

Class 0 Read-only; factory-programmable Class 1 Write-once, read manyClass 2 Fully re-writable Class 3 Active Tag (fully re-writable) Class 4Relay Tag - can communicate with other Tags

RFIDs in this invention perform the functionality of all five classes,providing a superset of the foregoing, and constitute a new class ofRFID.

Further objects and advantages of this invention are reduction inphysical size of RFID Tags, thus enabling them to be placed on a greatvariety of items such as the typical item on a supermarket shelf;greater ease of handling, storage, and application; greater range;ability to operate without a direct path between Tag and Reader;improved reliability and dependability of operation; improved mechanicalintegrity; capability of localization of the Tag; low power of datatransmission, in downlink or uplink, low complexity of hardware; lowcost of manufacture.

SUMMARY OF THE INVENTION

A method and system for RFIDs whereby the Tag and Reader, the latterotherwise known as interrogator, scanner or energizer, communicate databy means independent from that used for transfer of energy from Readerto Tag. A narrowband carrier, or continuous wave (CW), with or withoutdata, is used to energize the Tag, while a wideband, low-power signal,typically ultra wideband, is used for the exchange of data betweenReader and Tag. The asymmetry established is leveraged to enable theReader to emit energy to power the Tag at a much higher level thanpossible using the same band, or low power communications duringsubsequent data communication with the Tag. The disparity in powerlevels between these two, narrowband and wideband, is typically athousand times, most often more. This scheme enables the Reader toefficiently energize the Tag using any available narrowband frequency,such as those on in the 5.15-5.85 GHz portion of the spectrum, or the2.4-2.4835 GHz, or the 902-928 MHz (in Europe 869.4-869.65 MHz) wherethe Reader can output power in the range of Watts. Then Tag and Readercan communicate data in wideband, low-power mode, notably over a portionor over all of the ultra wideband spectrum 3.1-10.6 GHz, where theoutput power necessary is in the range of well under a milliwatt.

The combination of relatively high power to energize the Tag, and verylow power to communicate data to and from the Tag, relieves the Tag fromhaving to communicate by reflection to the Reader, and enables theestablishment of a true radio link upstream from Tag to Reader (as wellas of course downstream). This radio transmission uplink consists of asignal generated and transmitted by the Tag to the Reader, as opposed toreflections in use in prior art, and enables a greater degree ofreliability of the communication link, avoids the double path loss,enables longer range communication between Tag and Reader, uses asmaller Antenna, and hence makes for a smaller Tag.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the RF “gun” in the Reader energizing the Microchip onthe RFID Tag. This process is one of transfer of energy and takes placein a manner and on a band different from the process used for datatransfer. For this process the Reader contains a narrowband transmitter,but the RFID Microchip needs no receiver as used traditionally incommunications. Instead, the narrowband transmission energy is receivedby the Microchip and directly routed to a power supply circuit whichtakes the waveform, rectifies and shapes it, and turns it into a DCvoltage level for the brief duration of processing on the RFID Microchipand communication between the Reader and Tag.

FIG. 2 schematically depicts the Antenna and power supply circuit, thelatter being part of the RFID Microchip. The waveform from the Readerarrives via the Antenna, the latter depicted as a pair of solid linesfor simplicity. Chief among the various antennas in this invention is apatch Antenna. The converter is used to perform a regulatory functionand to step up or step down the voltage to a level appropriate, such as1.8 volts, for the circuitry inside the integrated circuit constitutingthe Microchip to operate. One embodiment of the converter is illustratedby the optional zener diode. It acts as a single-component, inexpensivestep-down converter and regulator for applications where the requirementon the efficiency of power conversion is more relaxed, these beingprimarily low-range applications.

FIG. 3 depicts the Reader and the Tag exchanging information by alow-power wideband method, different from that by which the Readerenergizes the Microchip on the Tag. Typically this method is ultrawideband, and the RFID Microchip and Reader each contain a UWBtransceiver and communicate by means of ultra wideband transmission andreception.

FIG. 4 depicts simultaneous energization and exchange of informationbetween the Reader and Tag.

FIG. 5 depicts three-dimensional localization of an item, of unknownposition, which has an RFID Tag, by three Readers. A plan view, thez-axis is looking into the page.

DETAILED DESCRIPTION OF THE INVENTION

The Reader powers the Tag by transmission of a relatively high powernarrowband carrier frequency, but communicates to/from the Tag bycomparatively low power means over a wideband portion of the frequencyspectrum. The energization of the Microchip on the Tag takes place by adifferent mechanism and uses a different method than is used forcommunication between Reader and Tag.

Reader and Tag communicate data by means of ultra wideband transmissionand reception on a portion or all of the 3.1-10.6 GHz band. The totalpower for transmission by this means, in either direction, but inparticular from Tag to is Reader, is well under a milliwatt. The Antennafor operation at this power is a small patch antenna. The size of thepatch Antenna has already been demonstrated with antennas ofapproximately 19 mm by 25 mm in size, 17 mm by 20 mm in size, 8 mm by 10mm in size, and 6 mm by 8 mm in size. The low power consumption of theMicrochip means that the energy capture and storage devices on board areof small size and low-power. The size affects the silicon area, thusphysical area, and cost of the integrated circuit constituting theMicrochip.

For the purposes of this invention what is intended by a narrowbandcarrier is a continuous or hopping wave with or without modulated datawith a maximum bandwidth of 150 MHz, and what is intended by a widebandsignal is one which has a bandwidth of at least 250 MHz, and what isintended by an ultra wideband signal, at least as initial practice, isone which has a bandwidth of at least 500 MHz.

Were the power needed by the Tag to be transferred remotely by theReader to Tag by the same wideband means as data is communicated, saidpower would suffer such path loss as to render it wholly insufficientfor the purpose of energizing the Microchip when it arrives at theAntenna. The gain of the directional Antenna incorporated in the Readerto effectively boosts its output power for the Tag to higher levels. Thetransfer of energy takes place on a suitable available narrowband. As afirst implementation this invention will use carriers in the 5.15-5.85GHz band, in the 2.4 GHz band, or in the 900 MHz (in Europe 869.4-869.65MHz) band. The Reader thus couples well over a thousand times moreenergy to the Tag using this method than the energy utilized by the Tagfor communication to the Reader. The narrowband carrier is used forenergization of the Tags, while communication between Tag and Readertakes place by means of ultra wideband. The power emanated from theReader is sufficient for RFID read or write operations involving the Tagwith no energy is storage necessary. Sample link budgets yieldsufficient power at a range of over 50 feet to energize the Tag tocommunicate uplink and receive and process communication downlink fromthe Reader.

An inductive power conversion circuit or a capacitive charge pump usinglow forward voltage drop schottky diodes is used to convert the powerthus received by the Tag from the Reader to a useful supply voltage forthe Microchip's internal circuitry, typically in the range 1.2-1.8Volts.

Optionally for some applications, when higher transmission power, suchas for the purposes of extending the range even further are desirable,than the power level available in real time to the Tag, a capacitor isincorporated onto the Tag. Thus prior to communication, for a briefperiod the Microchip on the Tag first absorbs and stores energy aboardthe capacitor from the Reader. Then, during communication, the Microchipuses a greater amount of power than would be available to itcontinuously in real-time mode from the Reader energizing it. The sizeof the capacitor used is described below:

The energy stored aboard a capacitor being E=½ CV², gives us thecapacitance needed, C, as being equal to 2 E/V². Power equals averageenergy spent per unit time, and thus the energy needed to be storedequals this average power multiplied by time. For the Microchip tooperate at a steady level of 2 microwatts over the typical period ofabout 8 milliseconds necessary to establish communications and transmitits contents to the Reader, the energy needed would be estimates as:2 μW×8 ms=16 nanojoules.

Thus the value of the capacitor, for circuit operation at 1.8 V (acurrent widely used supply voltage in ICs), allowing for a drop of onevolt from the unregulated voltage to the supply output, for a total of2.8V, is as follows:C=2 E/V²=2×(16 nJ)×(2.8 V)² 250.88 nF≈10.25 μF

Such values of capacitance is available in the industry-standard smallform-factor “1206” packages, measuring 1 mm by 3.5 mm, as a commodityitem at very low estimated additional cost to the Tag, as of thiswriting a fraction of a cent, with handling and assembly added togetherall still below half a cent. Capacitors at many times the 0.25microfarad value are also available at approximately the same cost andin the same or similarly small package which may be used preferably.Thus a capacitor may optionally be integrated on-board the Tag, as maybe desirable in the future, to enable operation at a higher power level,to extend the period of operation in large memory applications, toextend range for example for radiolocation purposes, to increaseavailable processing power for example for coding/encoding, or toenhance other capabilities of the Tag.

In addition, optionally, to further extend operational range such as forradiolocation purposes, beyond where the Reader could reach to power theTag, a solar cell, a battery, or a much larger storage capacitor, of theorder of Farads, may be incorporated onto the Tag. The solar cell wouldbe used in combination with either a capacitor or a battery when nightoperation is required. The added cost, as of this writing, will be inthe 50 cent range and comparable to battery-assisted Tags.

In an application where line of sight is available, optionally, theReader will emit a beam of electromagnetic radiation, such as in theinfrared or visible bands, to power the Tag.

The process of capture and conversion of this energy into a usefulsupply for the operation of the circuitry on the Microchip, is takenconservatively as 50% efficient (consider for comparison the 80-95%typical efficiency of commodity power converters in the electronicsindustry readily available from manufacturers).

The power necessary to operate the circuitry aboard an RFID Tag is lessthan a few microwatts. As an example, in 2001 RFIDs implemented in aninexpensive 0.5 micron CMOS process required 5 microwatts for operation.

For locating the position of a Tag the following method is employed. Thesystem comprised of the RFID Tag and the RFID Reader or Readers, bymeans of communication of a known test signal from Reader to Tag andback, performs measurement of time of flight, allows for a knownprocessing delay till response issues from Tag. It then determines thedistance between Reader and Tag by subtraction of the processing delayfrom half the round-trip time of flight and multiplication of the resultby the speed of light. It then calculates, employing proper algorithmsinvolving the solving of simultaneous equations resultant from theintersection of circles or spheres centered at each Reader whose radiusis the distance thus measured, and locates the two dimensional orthree-dimensional position of an RFID Tag.

The asymmetric means of energization and communication makes possible aMicrochip on the Tag with relatively low power usage as compared to thepower transmitted by the Reader. This asymmetric scheme, combinednarrowband energization and wideband communication, and itsimplementation, achieves this invention's major advantages over existingRFID systems, namely:

-   1) Longer range. Due to the establishment of an uplink from Tag to    Reader employing a signal generated by the Tag, and hence lower path    loss, combined with an efficient method of remotely powering the Tag    and other techniques, the possible range of operation from Reader to    Tag is substantially increased as compared to prior art.-   2) Much smaller Antenna size. As shown above, being not more than 26    mm by 19 mm, thus giving a smaller Tag than prior art. The smaller    Tag results in wider applicability and greater ease of handling,    storing and application to objects.-   3) Flexibility in Orientation. Orientation of Tag to Reader is not    required, nor a direct path from Tag to Reader, The ultra wideband    signal of communicating data between Reader and Tag in this    invention, allows and benefits from reflections in the path from Tag    to Reader and vice versa. Thus, firstly, orientation of the Tag    toward the Reader is not necessary and, secondly, a direct path    between Tag and Reader is not required. The Tag and Reader can thus    operate in cluttered environments, though when in such environments    the range will accordingly to the number and kind of objects in    between be reduced compared to free space.-   4) Reliability and dependability. Due to the establishment of a true    radio link from Tag to Reader, with a signal of energy originated by    the Tag and transmitted to the Reader, a reliable and dependable a    form of wireless communication, is achieved comparable to any other,    such as wireless LAN or mobile telephone, both of which likewise    possess a true uplink rather than use reflections.-   5) Mechanical Integrity. Due to the rigid patch Antenna employed for    communication unlike prior art which uses a large flexible sheet,    the Microchip on the Antenna, being typically a integrated circuit,    does not bend to result in micro cracks or breakage.

In an embodiment, as depicted in FIG. 4, an RFID Reader 106 equippedwith a directional antenna 107 with gain, a narrowband transmitter 108,and an ultra wideband (UWB) transceiver 109, transmits a narrowbandcarrier 105 to energize an RFID Tag 103. The RFID Tag's Antenna 102which may have negative or positive gain, receives energy from thistransmission, and transfers said energy to the Tag's Microchip 101. TheTag's Microchip 101 thus enters awake mode from asleep, establishescommunication 121 with and transmits via its UWB transceiver 104 thecontents of its memory to the Reader 106. The reader receives thisinformation from the Tag 103, and optionally updates the contents of theTag's Microchip's memory by establishing communication 122 with andtransmitting a 500 MHz wide ultra wideband signal overlapping thenarrowband frequency to the Tag.

In an embodiment as depicted in FIG. 5, a test signal known to the Tag133 is sent to the Tag by one of several Readers 130. The Tag, uponrecognizing said signal, issues an acknowledgment known to the Reader130, which measures the round-trip time. The response time, orprocessing delay, of the Tag is known by calculation or measurement andhas been pre-recorded in the Reader 130 at time of manufacture. TheReader then subtracts this processing delay from the round-trip time forits reply, divides the result obtained by two, multiplies this result bythe speed of light, and obtains the distance 134 from it to the Tag 133.For a three-dimensional localization of the Tag, the procedure isrepeated by at least two more Readers 131 and 132, and their distances135 and 136, respectively, from the Tag similarly measured, but where atwo-dimensional localization of the Tag may suffice, the procedure isrepeated by at least one more Reader. The distance of each Reader fromthe Tag is thus determined, which distance is the radius of a circlecentered at the respective Reader. Thus, in a Cartesian coordinatesystem (x, y, z), with the location of the first Reader 130 regarded asthe origin, the location of the second Reader 131 as (a₁, b₁, c₁), andthat of the third Reader 132 as (a₂, b₂, c₂), and their radiirespectively r, r₁, r₂, for a three-dimensional localization threeequations are obtained:x ² +y ² +z ² =r ²(x−a ₁)²+(y−b ₁)²+(z−c ₁)² =r ₁ ²(x−a ₂)²+(y−b ₂)²+(z−c ₂)² =r ₂ ²thus giving three simultaneous equations, sufficient to solve for thevalues of x, y, z, which lie at the intersection of the three spheresthus obtained, and define the location of the Tag 133. As these arequadratic equations a pair of values may be obtained for each unknown,and one of them would lie outside the range of practice. As analternative means to recognizing which lies outside said range, anadditional Reader may be used, whereby four simultaneous equations wouldbe available for the solution of three unknowns.

Where only a two-dimensional positioning is required, a minimum of twoReaders would be used, with the equations then being:x ² +y ² =r ²(x−a ₁)²+(y−b ₁)² =r ₁ ²

Again as these are quadratic equations a pair of values may be obtainedfor each unknown, and one of them would lie outside the range ofpractice. As an alternative means to recognizing which lies outside saidrange, an additional Reader may be used, whereby three simultaneousequations would be available for the solution of two unknowns.

In an embodiment, as depicted in FIG. 2, an RF waveform from an RFIDReader arrives at the Antenna 102 of an RFID Tag. The waveform causesthe flow of electrical energy from the Antenna 102 to the diodes 113-116which rectify the electrical waveform and pass it to a power converter117 which thereby converts the received waveform to a higher or lowervoltage usable by the Tag's apparatus. A capacitor 118 further smoothesthe voltage output by converter 117. In cases the usual voltage outputby the diodes 113-116 is usable without conversion to a significantlyhigher or lower voltage, for the operational voltage needed a zener 119is selected, and the zener in conjunction with the capacitor 118performs the task of providing a stable supply at desired voltage.

A method for Radio Frequency Identification (RFID), is thus givenwhereby an RFID Reader remotely energizes a Tag and the Reader and Tagthereby exchange information, wherein the means by which the RFID Tagis, or a plurality of RFID Tags are, energized by the RFID Reader orReaders is independent of the means by which Tag and Reader communicateinformation to each other.

The means by which the Tag is, or a plurality of RFID Tags are,energized by the Reader or Readers is that of a narrowband stationary orhopping carrier which need carry no data, and the means of transmissionand reception by which the Tag or a plurality of Tags and the Reader orReaders communicate is that of low-power narrowband or wideband.

The means of transmission and reception by which Tag and Readercommunicate information is that of an ultra wideband signal, which maybe pulsed, carrier-based or an orthogonal frequency-divisionmultiplexing ultra wideband signal, may include a rake receiver, andwherein a patch Antenna, or Ultra Wideband Antenna, upon which ismounted an integrated circuit, together comprise the RFID Tag.

A narrowband stationary or hopping carrier in the 5.15-5.85 GHzfrequency range, or the 2.4-2.4835 GHz range, or the 902-928 MHz range,or the 869.4-869.65 MHz range, or other available frequency range, whichneed carry no data, is transmitted by the Reader energizing the Tag orTags.

The wideband signal occupies a sufficiently small portion of thespectrum, overlapping or near the narrowband carrier frequency intendedto be emanated by the Reader, thus allowing the Tag to be operationalwith a single Antenna capable of receiving both the narrowbandstationary or hopping carrier and receiving/transmitting the widebandsignal.

The wideband signal may be an ultra wideband signal occupying a smallportion of the 3.1-10.6 GHz spectrum, at least 500 MHz wide, overlappingor near the narrowband carrier frequency intended to be transmitted bythe Reader, thus allowing the Tag to be operational with a singleAntenna capable of receiving both the narrowband stationary or hoppingcarrier and receiving/transmitting the wideband signal.

The ultra wideband signal occupies a small portion of the 3.1-10.6 GHzspectrum, at least 500 MHz wide, starting at the 5.725-5.85 GHz band,and overlapping a portion or all of said band, whereby the narrowbandcarrier frequency transmitted by the Reader which employs a directionalantenna with gain also lies within said band, thus allowing the Tag tobe operational with a single Antenna capable of receiving both thenarrowband stationary or hopping carrier and receiving/transmitting theultra wideband signal.

The ultra wideband signal occupies a small portion of the 3.1-10.6 GHzspectrum, at least 500 MHz wide, overlapping or near the narrowbandcarrier frequency intended to be transmitted by the Reader, thusallowing the Tag to be operational with a single Antenna capable ofreceiving both the ultra wideband signal and the narrowband carrier.

The apparatus by which the RFID Reader subsystem performs its functionof energization of the RFID Tag may reside in a physical housingdistinct from the apparatus by which the RFID Reader subsystemcommunicates information with the RFID Tag or plurality of Tags, the twohousings being separately located, enabling the placement of multipleenergizers strategically where Tags are to be powered and read orwritten to.

The apparatus of the Reader or Readers energizing and communicatinginformation with the Tag or plurality of Tags is equipped with adirectional antenna with gain, whereby the power output of the carrierfrom the Reader or Readers may be lowered in proper proportion accordingto the gain of said directional antenna.

The apparatus of the Tag employs low forward voltage drop diodesincluding, but not limited to, Schottky diodes, and/or employs acapacitive charge pump or inductive switching circuit to convertreceived power from the Reader or Readers to useful supply voltage forits circuitry and/or the apparatus in the Tag employs a zener diode ordiodes to regulate and stabilize said supply voltage for the Tag'scircuitry.

The apparatus of the Tag employs memory, electrically-erasableprogrammable read-only memory or non-volatile random access memory, torecord information it may receive from the Reader or Readers, or tostore information at the time of manufacture.

The Reader through its ports operates wireless or wireline links toother equipment that constitutes part of the enterprise system of anorganization which may include a factory, warehouse, department store,retail outlet, or offices, for the purpose of relaying information andcommunicating to/from the Tag, said ports and links being separate anddistinct from the Reader's links with the Tag.

The RFID Tag may employ within its apparatus an integrated circuithaving radio frequency, analog and digital circuitry.

The RFID Tag may employ within its apparatus for the purposes ofprocessing data, memory and logic control, a state machine or amicrocoded engine or a microcontroller or a central processing unit or adigital signal processor.

The means by which the RFID Tag is, or a plurality of RFID Tags are,energized by the Reader or Readers may be augmented or replaced by asolar cell or solar cells incorporated on the apparatus of the RFID Tagor may be augmented or replaced by a battery incorporated within theapparatus of the RFID Tag.

The means by which the RFID Tag is, or a plurality of RFID Tags are,energized by the Reader or Readers, is, where a line of sight isavailable, augmented or replaced by a beam of electromagnetic radiationin the infra-red or visible or other available part of the spectrum.

The means by which the RFID Tag is, or a plurality of RFID Tags are,energized by the Reader or Readers may be augmented by apparatus aboardthe RFID Tag incorporating a capacitor for the storage of energyreceived from the Reader, for use by the circuitry aboard the Tag or fortransmission.

The system comprised of the RFID Tag or plurality of Tags and the RFIDReader or Readers, by means of communication of a known test signal fromReader to Tag and back, performs measurement of time of flight, allowsfor a known processing delay till response issues from Tag, determinesdistance between Reader and Tag by subtraction of said processing delayfrom half the round-trip time of flight and multiplication of the resultby the speed of light, and by calculation employing proper algorithmsinvolving the solving of simultaneous equations resultant from theintersection of circles or spheres centered at each Reader whose radiusis the distance thus measured from said Reader to Tag to be localized,locates the two dimensional or three-dimensional position of an RFID Tagor Tags.

A plurality of RFID Tags energized by a Reader or Readers communicateinformation to each other and act as relays for one another in a meshnetwork, thus allowing local networking and in addition extending therange possible between a given RFID Reader and a given RFID Tag.

Possible collisions in transmission to the Reader or Readers from aplurality of RFID Tags that may be energized simultaneously is preventedor minimized by an anti-collision algorithm or protocol such asstatistically randomized timing of transmissions precoded into theapparatus of the Tags and the Reader, or wherein the RFID reader is ableto selectively address or turn off, temporarily or permanently,individual Tags.

What is claimed is:
 1. An asymmetric bandwidth communication systemcomprising: a. a powered interrogator/reader downlink transmitting in anon-TDCIR signal; b. a transponder or tag receiving said non-TDCIRsignal to at least partially or wholly power said tag; c. said non-TDCIRdownlink transmission from said interrogator/reader interrogating andinstructing said transponder to broadcast data; d. said transponderuplink communicating with said interrogator/reader using time domaincarrierless impulse radio (TDCIR) having ultra wide band width frequencyspectrum of a short time duration pulse; and e. said poweredinterrogator/reader receiving the TDCIR ultra wide band short timeduration pulse uplink communication; whereby data is communicated fromsaid transponder or tag to said interrogator/reader using very littletransponder power and an uncomplicated low cost transponder design thatlends itself to manufacturability with greater ease andcost-effectiveness.
 2. An asymmetric bandwidth communication system asrecited by claim 1, wherein said interrogator/reader communicates withsaid transponder or tag at a frequency of range of approximately 850-960MHz, or approximately centered on 915 MHz or on any of the ISM or UNIIbands.
 3. An asymmetric bandwidth communication system as recited byclaim 1, wherein said interrogator/reader communicates with saidtransponder or tag to determine the distance or range of said tag, andwherein said data on distance or range from three or more saidinterrogator/readers may be combined using triangulation to obtain thetwo dimensional position of said transponder or tag, or wherein saiddata on distance or range from three or more said interrogator/readersmay be combined using triangulation to obtain the three dimensionalposition of said transponder or tag.
 4. An asymmetric bandwidthcommunication system as recited by claim 1, wherein said transponder ortag additionally communicates with said interrogator/reader usingconventional RF communication and said transponder or tag is may beequipped with onboard additional power source.
 5. An asymmetricbandwidth communication system as recited by claim 1, wherein saidtransponder or tag communicates with said interrogator/reader for RFcommunication and TDCIR communication by a single common antenna, whichmay be a patch antenna or an ultra wideband antenna.
 6. An asymmetricbandwidth communication system as recited by claim 1, wherein saidinterrogator downlinks to said transponder or tag by RF and TDCIR tocommunicate data and said transponder receiving said RF by first antennaand receiving said pulsed ultra wideband communication by a secondantenna and uplinking with said interrogator/reader by pulsed ultrawideband communication by said second antenna.
 7. An asymmetricbandwidth communication system comprising: a. a poweredinterrogator/reader capable of receiving and decoding TDCIR signals; b.a transponder or tag capable of generating and transmitting data viaTDCIR signals which transponder or tag is powered by battery, solar cellaugmented with capacitor of sufficient capacitance to last expected darkperiods, or long-life capacitor or is equipped with other on-boardsource of power; c. said non-TDCIR downlink transmission from saidinterrogator/reader interrogating and instructing said transponder tobroadcast data; d. said transponder communicating uplink using timedomain carrierless impulse radio (TDCIR) having ultra wide band widthfrequency spectrum and a short time duration pulse; e. said poweredinterrogator/reader receiving and decoding the TDCIR ultra wide bandshort time duration pulse uplink communication from said transponder; f.and wherein said transponder or tag may in addition communicate to saidinterrogator/reader using conventional (non-TDCIR) RF transmissions.whereby data is communicated from said transponder or tag to saidinterrogator/reader using very little transponder power and anuncomplicated low cost transponder design that lends itself tomanufacturability with greater ease and cost-effectiveness.
 8. Themethod of claim 1, wherein a narrowband stationary or hopping carrier inthe 5.15-5.85 GHz frequency range, or the 2.4-2.4835 GHz range, or the902-928 MHz range, or the 869.4-869.65 MHz range, or other availablefrequency range, which need carry no data, is transmitted by the Readerthus energizing the Tag or Tags.
 9. The method of claim 1, whereby thecarrier-based signal's frequency overlaps the ultra wideband signal'sfrequency spectrum or is near that frequency spectrum, thus allowing theTag to be operational with a single Antenna capable of receiving boththe carrier-based stationary or hopping signal and receiving and/ortransmitting the ultra wideband signal.
 10. The method of claim 1,whereby the Reader employs one or more directional antennae, also knownas constant aperture antenna, which intrinsically have gain and mayserve one or both of said signals, whereby in the case of thecarrier-based signal the power output of the carrier from a Reader maybe lowered in proper proportion according to the gain of saiddirectional antenna.
 11. The method of claim 1, whereby the physicalmechanism by which the RFID Reader performs its function of energizationof the RFID Tag resides in a housing or enclosure distinct from andlocated separately from the physical mechanism by which the RFID Readercommunicates information with the RFID Tag or plurality of Tags, thusenabling the placement of multiple energizers strategically where Tagsare to be powered and read from or written to.
 12. The method of claim1, whereby the integrated circuit of the Tag employs low forwardvoltage-drop diodes, or equivalent components, including, but notlimited to, Schottky diodes, and/or employs a capacitive charge pump orinductive switching circuit to convert received power from a Reader orenergizer to a power supply with useful voltage for its circuitry andthe integrated circuit of the Tag employs a zener diode or diodes orequivalent means to regulate and stabilize said voltage for use by therest of the Tag's integrated circuit.
 13. The method of claim 1, wherebythe integrated circuit of the Tag employs memory, electrically-erasableprogrammable read-only memory or non-volatile random access memory, torecord information it may receive from the Reader or Readers, or tostore information at the time of manufacture, and thus be able to retainsuch information in the absence of power.
 14. The method of claim 1,whereby the Reader, receiving ultra wideband information from the Tags,through its ports operates wireless or wireline communication links toother equipment, where said equipment constitutes part of the enterprisesystem of an organization which may include a factory, warehouse,department store, retail outlet, or offices, for the purpose of relayinginformation aboard Tag(s) to said system, and communicating between saidsystem and the Tag, wherein said ports and links are separate anddistinct from the links between Reader and Tag.
 15. The method of eitherclaim 1, whereby the RFID Tag employs within its integrated circuit oneor more integrated components having radio frequency, analog and digitalcircuitry and means for processing information, said circuitry and othermeans comprising the RFID Tag's integrated circuit.
 16. The method ofclaim 1, whereby the RFID Tag employs within its integrated circuit, forthe purposes of processing data: memory, logic control, state machine,microcoded engine, microcontroller, central processing unit, digitalsignal processor.
 17. The method of claim 1, wherein the means by whichthe RFID Tag is, or a plurality of RFID Tags are, energized is augmentedor replaced by a solar cell incorporated on the integrated circuit ofthe RFID Tag or said method is augmented or replaced by a batteryincorporated on the integrated circuit of the RFID Tag, or where a lineof sight is available, said method is augmented or replaced by a beam ofelectromagnetic radiation in the infra-red or visible or other availableand permissible part of the spectrum, or where said method is augmentedby the Tag or its integrated circuit incorporating a capacitor for thestorage of energy received, for use at the time or for transmissionafter energization has ceased.
 18. The method of claim 1, wherein thesystem comprised of the RFID Tag or plurality of Tags and the RFIDReader or Readers, by means of communication of a known test signal fromReader to Tag and back, performs measurement of time of flight, allowsfor a known processing delay until response issues from Tag, determinesdistance between Reader and Tag by consideration of time of flight andthe speed of light, and by calculation employing proper algorithmsinvolving the solving of simultaneous equations locates thetwo-dimensional or three-dimensional position of an RFID Tag or Tagsdesired to be localized, which emitted said test signal.
 19. The methodof claim 1, wherein the system comprised of the RFID Tag or plurality ofTags and the RFID Reader or Readers, by means of communication of aknown test signal from Tag which is then received by Readers, calculatesthe time difference of arrival of said signal at various Readers andfrom that information, and speed of light, and by calculation employingproper algorithms involving the solving of simultaneous equations thuslocates the two dimensional or three-dimensional position of the RFIDTag or Tags desired to be localized, which emitted said test signal. 20.The method of claim 1, wherein a plurality of RFID Tags communicateinformation to each other and act as relays for one another andcommunicate information in a mesh network, thus enabling the networkingof Tags in the absence of Readers as well as extending the rangepossible between a given RFID Reader and a given RFID Tag.
 21. Themethod of claim 1, wherein possible collisions in transmission to theReader or Readers from a plurality of RFID Tags that may be energizedsimultaneously is prevented or minimized by an anti-collision algorithmor protocol with statistical randomized timing of transmissions precodedinto the integrated circuit of the Tags and into the Reader forexpecting the same, or wherein the RFID reader is able to selectivelyaddress or turn off, temporarily or permanently, individual Tags. 22.The method of claim 17, wherein a plurality of Tags thus energizedcommunicate information to each other and act as relays for one anotherin a mesh network, thus enabling the networking of Tags in the absenceof Readers as well as extending the range possible between a given RFIDReader and a given RFID Tag.
 23. The method of claim 7, wherein anarrowband stationary or hopping carrier in the 5.15-5.85 GHz frequencyrange, or the 2.4-2.4835 GHz range, or the 902-928 MHz range, or the869.4-869.65 MHz range, or other available frequency range, which needcarry no data, is transmitted by the Reader thus energizing the Tag orTags.
 24. The method of claim 7, whereby the carrier-based signal'sfrequency overlaps the ultra wideband signal's frequency spectrum or isnear that frequency spectrum, thus allowing the Tag to be operationalwith a single Antenna capable of receiving both the carrier-basedstationary or hopping signal and receiving and/or transmitting the ultrawideband signal.
 25. The method of claim 7, whereby the Reader employsone or more directional antennae, also known as constant apertureantenna, which intrinsically have gain and may serve one or both of saidsignals, whereby in the case of the carrier-based signal the poweroutput of the carrier from a Reader may be lowered in proper proportionaccording to the gain of said directional antenna.
 26. The method ofclaim 7, whereby the physical mechanism by which the RFID Readerperforms its function of energization of the RFID Tag resides in ahousing or enclosure distinct from and located separately from thephysical mechanism by which the RFID Reader communicates informationwith the RFID Tag or plurality of Tags, thus enabling the placement ofmultiple energizers strategically where Tags are to be powered and readfrom or written to.
 27. The method of claim 7, whereby the integratedcircuit of the Tag employs low forward voltage-drop diodes, orequivalent components, including, but not limited to, Schottky diodes,and/or employs a capacitive charge pump or inductive switching circuitto convert received power from a Reader or energizer to a power supplywith useful voltage for its circuitry and the integrated circuit of theTag employs a zener diode or diodes or equivalent means to regulate andstabilize said voltage for use by the rest of the Tag's integratedcircuit.
 28. The method of claim 7, whereby the integrated circuit ofthe Tag employs memory, electrically-erasable programmable read-onlymemory or non-volatile random access memory, to record information itmay receive from the Reader or Readers, or to store information at thetime of manufacture, and thus be able to retain such information in theabsence of power.
 29. The method of claim 7, whereby the Reader,receiving ultra wideband information from the Tags, through its portsoperates wireless or wireline communication links to other equipment,where said equipment constitutes part of the enterprise system of anorganization which may include a factory, warehouse, department store,retail outlet, or offices, for the purpose of relaying informationaboard Tag(s) to said system, and communicating between said system andthe Tag, wherein said ports and links are separate and distinct from thelinks between Reader and Tag.
 30. The method of claim 7, whereby theRFID Tag employs within its integrated circuit one or more integratedcomponents having radio frequency, analog and digital circuitry andmeans for processing information, said circuitry and other meanscomprising the RFID Tag's integrated circuit.
 31. The method of claim 7,whereby the RFID Tag employs within its integrated circuit, for thepurposes of processing data: memory, logic control, state machine,microcoded engine, microcontroller, central processing unit, digitalsignal processor.
 32. The method of claim 7, wherein the means by whichthe RFID Tag is, or a plurality of RFID Tags are, energized is augmentedor replaced by a solar cell incorporated on the integrated circuit ofthe RFID Tag or said method is augmented or replaced by a batteryincorporated on the integrated circuit of the RFID Tag, or where a lineof sight is available, said method is augmented or replaced by a beam ofelectromagnetic radiation in the infra-red or visible or other availableand permissible part of the spectrum, or where said method is augmentedby the Tag or its integrated circuit incorporating a capacitor for thestorage of energy received, for use at the time or for transmissionafter energization has ceased.
 33. The method of claim 7, wherein thesystem comprised of the RFID Tag or plurality of Tags and the RFIDReader or Readers, by means of communication of a known test signal fromReader to Tag and back, performs measurement of time of flight, allowsfor a known processing delay until response issues from Tag, determinesdistance between Reader and Tag by consideration of time of flight andthe speed of light, and by calculation employing proper algorithmsinvolving the solving of simultaneous equations locates thetwo-dimensional or three-dimensional position of an RFID Tag or Tagsdesired to be localized, which emitted said test signal.
 34. The methodof claim 7, wherein the system comprised of the RFID Tag or plurality ofTags and the RFID Reader or Readers, by means of communication of aknown test signal from Tag which is then received by Readers, calculatesthe time difference of arrival of said signal at various Readers andfrom that information, and speed of light, and by calculation employingproper algorithms involving the solving of simultaneous equations thuslocates the two dimensional or three-dimensional position of the RFIDTag or Tags desired to be localized, which emitted said test signal. 35.The method of claim 7, wherein a plurality of RFID Tags communicateinformation to each other and act as relays for one another andcommunicate information in a mesh network, thus enabling the networkingof Tags in the absence of Readers as well as extending the rangepossible between a given RFID Reader and a given RFID Tag.
 36. Themethod of claim 7, wherein possible collisions in transmission to theReader or Readers from a plurality of RFID Tags that may be energizedsimultaneously is prevented or minimized by an anti-collision algorithmor protocol with statistical randomized timing of transmissions precodedinto the integrated circuit of the Tags and into the Reader forexpecting the same, or wherein the RFID reader is able to selectivelyaddress or turn off, temporarily or permanently, individual Tags. 37.The method of claim 32, wherein a plurality of Tags thus energizedcommunicate information to each other and act as relays for one anotherin a mesh network, thus enabling the networking of Tags in the absenceof Readers as well as extending the range possible between a given RFIDReader and a given RFID Tag.